Proximity sensor devices (also commonly called touch sensor devices) are widely used in a variety of electronic systems. A proximity sensor device typically includes a sensing region, often demarked by a surface, in which input objects can be detected. Example input objects include fingers, styli, and the like. The proximity sensor device can utilize one or more sensors based on capacitive, resistive, inductive, optical, acoustic and/or other technology. Further, the proximity sensor device may determine the presence, location and/or motion of a single input object in the sensing region, or of multiple input objects simultaneously in the sensor region.
The proximity sensor device can be used to enable control of an associated electronic system. For example, proximity sensor devices are often used as input devices for larger computing systems, including: notebook computers and desktop computers. Proximity sensor devices are also often used in smaller systems, including: handheld systems such as personal digital assistants (PDAs), remote controls, and communication systems such as wireless telephones and text messaging systems. Increasingly, proximity sensor devices are used in media systems, such as CD, DVD, MP3, video or other media recorders or players. The proximity sensor device can be integral or peripheral to the computing system with which it interacts.
One issue with some past proximity sensor devices is susceptibility to electrostatic discharge (ESD). In general, electrostatic discharge is an unwanted momentary flow of electric current. Electrostatic discharge can be caused by the presence of an electric field or through simple contact with an object at a different electric potential. One significant cause of electrostatic discharge is the build up of static electricity. When an object with the significant static electric build up is moved near to, or in contact with, a conductor, an electrostatic discharge current can be induced in the conductor. This current can then flow to any electronic components or devices that are electrically coupled to the conductor.
Electrostatic discharge can damage electronic devices, including proximity sensor devices. Because of this, proximity sensor devices must be protected from electrostatic discharge. This is commonly done with various ESD protection structures that are disposed around the proximity sensor device. Unfortunately, this protection can sometimes interfere with proximity sensor device operation. This problem is particularly acute in extended proximity sensor devices that are implemented to sense object presence at a significant distance from the device. Thus, there is a continuing need to develop proximity sensor devices with electrostatic discharge protection.